UV absorbing properties of extracts obtained from Canna flowers grown in Sri Lanka

Abstract

In this study, the UV absorbing properties of extracts of Canna flowers were evaluated using spectroscopic techniques and Mansur equation. The methanol and methanol: distilled water (1:1) extracts of red and yellow Canna flowers were analyzed for their SPF (Sun Protection Factor) by measuring UV absorbance of different concentrations in methanol. Dermatone® was used as a reference agent. Absorption data were obtained in the range of 290-320 nm, at every 5 nm and the SPF values were determines. All the extracts showed substantial UV absorbing abilities in the UVB region. The methanolic extract of Canna red flowers (0.8 mg mL- 1) has the highest mean SPF value 24.34 ± 0.02. All concentration series (0.2, 0.4, 0.6, 0.8 and 1.0 mg mL-1) of Canna red flowers have SPF ≥ 6. Phytochemical screening of crude methanolic extract of Canna red flowers revealed the presence of diterphenes, alkaloids, flavonoids, phenols and glycosides. These components were separated by Preparative Thin Layer Chromatography (PTLC). Flavonoid fraction from PTLC showed the highest mean SPF value of 13.66 ±0.05, while diterphenes, alkaloids, phenols and glycosides have the values of 6.56 ± 0.03, 0.11 ± 0.03, 11.60 ± 0.09 and 2.60 ± 0.08 respectively. The reference agent Dermatone® had SPF value of 25.72 ± 0.32. The results of this study indicate that the methanolic extract of Canna red flowers absorb the UVB radiation and possess sun protection ability against UVB radiation. The active components responsible for UV absorption could be isolated and used in sunscreen formulations.